The invention relates to a charge coupled semiconductor device. The device comprises a semiconductor body in which at least one charge transfer channel is defined at a major surface of the body. A system of electrodes is provided on the major surface. A reference signal can be applied to the electrodes to store charge in the channel. A clock signal can be applied to the electrodes to transport charge in the channel.
This application is related to applications entitled "Charge-coupled semiconductor device with dynamic control" Ser. No. 616,936, filed June 7, 1984) and "Charged Coupled Device Ser. No. 615,842, filed May 31, 1984) which are assigned to the same assignee as this application and which are incorporated by reference herein.
The devices, also known as CCD's (Charge-Coupled Devices), are used in various applications. For example, the devices are used as delay lines or memory elements. They are especially useful in image sensor devices.
The invention therefore relates more particularly to a charge coupled image sensor device in high a number of charge transfer channels are arranged. The channels are separated from each other and transport charge from a radiation-sensitive part to a memory part of the device.
Such image sensor devices are used in solid state cameras. In the cameras, the information stored in the memory part can be converted into a television signal, or may be temporarily stored, for example on a memory disk or memory tape.
Such an image sensor device is described in U.S. Pat. No. 3,909,803. The device is a charge coupled image sensor with four-phase transport. The various image elements are defined by groups of four electrodes. Charge is collected alternately under each of the four electrodes.
For this purpose, in a first exposure period charge is collected under a first set of electrodes. The collected charge is transferred to the memory part by applying suitable clock voltages to the electrodes. Subsequently, in a second exposure period charge is collected under a second set of electrodes located next to the first set. The collected charge is then also transferred to the memory part. Subsequently, the process is repeated with third and fourth sets of electrodes. Due to the fact that charges are collected separately under each set of electrodes, the resolution of the image sensor device is increased. However, this increased resolution is partly eliminated because charge carriers generated under the other electrodes are collected under the relevant electrode.
Moreover, the increased resolution is at the expense of a considerably increased sensing time. After charge has been collected under the first set of electrodes, this charge must first be drained to the memory part before charge can be collected under the next set. In this embodiment, the sensing time is therefore approximately quadrupled. Moreover, the four integration periods are separated in time so that in the memory part there is stored an image which is composed of scenes of four successive integration times.